This invention relates to hydrocarbon separation. More particularly, the invention concerns a process for separating a mixture of saturated hydrocarbons into normal paraffins, branched chain paraffins, and cyclic paraffins with the use of multiple molecular sieves of silicalite.
There are an abundance of processes known to separate classes of hydrocarbons using solid adsorbents. The most common adsorbents used for hydrocarbon separation are the crystalline aluminosilicates, the best known of which are the zeolites. The crystalline aluminosilicates function as molecular sieves. They contain pores having cross-sectional diameters which will accept certain molecules of a mixture of molecules while rejecting other molecules having different sizes, thereby separating the accepted molecules from the mixture.
A new molecular sieve adsorbent material known as silicalite has been disclosed and claimed in U.S. Pat. No. 4,061,724. The disclosed separation process discusses in general terms the separation of an organic compound from an aqueous solution. The separations exemplified in the above reference are n-butanol, methylcellosolve, methanol and phenol.
U.S. Pat. No. 4,455,445 discloses a separation of n-butane from isobutylene by the use of a silicalite molecular sieve. U.S. Pat. No. 4,486,618 discloses the separation of n-hexane from other paraffins having 6 carbon atoms using a silicalite molecular sieve. U.S. Pat. No. 4,455,444 discloses the separation of normal paraffins from a mixture of branched chain and cyclic paraffins by the use of a silicalite molecular sieve at 120.degree. C. to 140.degree. C. However, none of the above references disclose the separation of branched chain paraffins from cyclic paraffins.